Thermoresponsive device



Jan. 14, 1930.

H. D. JAMES ET AL THERMORESPONSIVE DEVICE Filed Feb. 1, 1927 2 Sheets-Sheet l WITNESSES:

INVENTORS ATTORNEY Jan. 14, 1930. H. D. JAMES ET AL 1,743,142

THERMORESPONS IVE DEVICE File 1927 2 Sheets-Sheet 2 WITNESSES: INVENTORS Patented Jan; 14, 1930 'l UNITED STATES PATENT OFFICE HENRY D. JAMES, OF EDGEWOOD, AND A UGUST .T. MOTTLAU, OF PITTSBURGH, PENN- SYLVANIA, ASSIGNORS TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COM- PANY, A CORPORATION OF PENNSYLVANIA THERMORESPONSIVE DEVICE Our invention relates to protective devices for electric circuits and ,particularly to thermally actuable devices.

An object of our invention is to provide vide a thermostatic means for actuating an electric switch that comprises a relatively fixed support and a member secured thereto having a high temperature coefficient of expansion relatively to that of the support.

Our invention comprises a thermo-responsive member and a circuit-controlling means actuated thereby. The thermo-responsive member is carried by a pair of supports and so restrained that it moves relatively to the supports upon change in thermal condition thereof.

In a preferred embodiment of our invention, the thcrmo-responsive member is sup ported in such bowed condition that longitu.- dinal expansion thereof results in lateral deflection of an intermediate portion.

A movement-multiplying mechanism is embodied in the circuit-controlling means that magnifies aneffect produced by changes in tion, ofa circuit-controlling meansembodied.

the thermal condition of the thermo-rcsponsive member, which conditions are utilized for actuating an electric switch that constitutes a part of the circuit-controlling means. The thermo-responslve member is provided with temperature-corrective means whereby the thermo-responsive member is maintained in substantially its initial shape or condition for all values of ambient temperature.

In the drawings, Figure 1 is a top View, partially in section, of a device embodying our invention.

2 is a top plan view, partially in secin the device illustrated in Fig. 1.

Fig. 3 is a front view, in elevation, of the device illustrated in Fig. 2.

Fig. 4 is a front plan view of the device illustrated in Fig. 2, taken on line IVIV thereof.

Fig. 5 is a top plan view of a detail embodied in the lever of the device illustrated particularly in Figs. 2 and 4.

Fig. 6 is an end view of the detail illustrated in Fig. 5.

Fig. 7 is a front view, in elevation, of a fulcrum embodied in the deviceillustrated in Figs. 1 to 4, inclusive.

Fig. 8 is a sectional fragmentary view, taken on the line VIII-VIII of Fig. 4.

In Fig. 1 of the drawings, a thermo-responsive device 11 comprises, in general, a thermostatic means 12 and a circuit-interrupting means 13.

The thermostatic means 12 comprises, in general, a support or base 14, a bar 15 attached thereto, a pair of supporting members 16 and 17 secured to the bar 15 and a thermo-responsive member or bus bar 18 carried by the members 16 and 17.

The bus bar 18 is preferably of the type employed in power-distribution systems and in switchboard construction and which is adapted to be traversed by currents of severalhundrcd amperes and upwards.

Since the supports 16 and 17 to which the ends of the bar 18' are secured, are not affected by heat and their position is relatively fixed, the bar 18, being preferably of a material having a high-temperature c0- eificient of expansion, will expand responsive to the heat generated by current flowing through it. Because the bar 18 is supported in an initially bowed condition (see Fig. 1), the expansion effected by current traversing the same will result in a lateral deflection of its middle portion in a direction towards the base 14, orv in the direction of its initial deflection.

The supporting member or base 14, in a preferred form of our'invention, is of a relatively non-expanding material, such as slate, that is usually embodied in switchboard structures.

In other forms of our invention, the base 14 maycomprise the walls of an electrically heated oven or the-walls of a refrigerator, it

being essential only that the walls have a relatively low temperature co-eflicient of expansion.

The bar 15 is attached to the base 14 and has one of its ends positively secured thereto by any suitable means, such as bolts or rivets 19. The other end of the bar 15 is provided with an elongated aperture 21 throughwhich a bolt 22 projects from the base 14 and is 10 slidably secured to the base 14 by means of base. One face of the. member 16 is provided with a slot27 in which one end of the member 18 is located, and an opening 28 is provided in an adjacent face thereof into which a bolt 29 extends to engage the member 18 to tightly hold the same in the member 16. The bolt 29 serves also as one terminal of the member 18. The supporting member 17 is secured tothe other end of the bar 15 by such means as 30 bolts 31, the heads of which are located in va recess 32 of the kbase 14, thus permitting this end of the bar 15 to move relatively to the face of the base. c j

One. face of the supporting'member 17 is provided with -a rectangular recess 33 in which a recessed'block 34 also of rectangular shape is located. One end of the member 18 extends into the recessed block 34 andlis secured therein by means of a'stud 35 that forms also a second terminalgfor the member 18.

A block 36 is located in the recess 33 between the supporting member 17 and the block 34 and has screw-threaded en agement with a bolt 37 that'passes through the mem her 17. By means of the bolt 37 and theblock Wards or away from the support 16,- thus varying the radius of curvature of themem ber-18. H fIf-"the member 18/ is to receive its thermal energy from the. temperature of the medium in which it is located, as distinguished from sage ofelectric current therethrou'gh, the temperaure-correctivebar 15 need not beem ployed. For examplef in the temperature c6ntroliof refrigerators or el'ectricallyheated I o'vens,the member 18 may be supported in' an archedcondi'tion by the walls of the device the'temperatu're of which is to be controlled. Thev effect ofthe ambient-temperature corrective bar 15 is to maintain the'central portion of themember 18 in a substantially fixed position. This is true-particularly when the 36, the slidable block .34 may be moved'tothe thermal energy received from the pas temperature co-efficient of expansionof thebar 15 and the member 18 are substantially equal. It the temperature of the bar 15 increases from ambient conditions, the member 18 will increase in temperature likewise, therefore, the bar 15 and the member 18 will expand substantially equal amounts in a linear direction. Since the bar 15 is free to move at one end, the member 18 may also move in the same direction, so that its central portion will remain at a substantially fixed distance from the bar 15.

I The circuit-interrupting means, illustrated more particularly in Figs; 2 to 4 inclusive, comprise a casing having a cover 38 and a base 39, a movement-multiplying mechanism 41 anda switch 42.

The cover 38 and the base 39 are provided with rabbeted edgeg for forming a rabbet joint, when occupying the position illustrated in Fig. 2, to form a casing.

The general outline of the casing is sub-- stantially that of a cylinderwhich is rectan gular in lateral section. One end of thehzasing is substantially circular and is provided with an opening 43 for-a purpose to be hereinafter set forth Y The base 39 is provided, at its circular end, with an annular flange 44 and a boss 45. The flange 44 is provided with holes 46 through which bolts may project for thepurpose of attaching the casing to the base 14.

The boss 45 has an opening 47 flierein for a purpose to be hereinafter set forth.

The bottom of the base 39 is provided with a.rectangular opening into which a switchsupporting base 48 of insulating material is located. A circular bushing 49, of elec-t ricinsulating material,-extends through another opening in the bottom of the base 39 and has screw threaded engagement therewith. A plurality of lugs"51 and 52 having tapped holes are also provided in the base, whereby thecover 38 may be secured to'the'base 39 by means ofbolts 53. v

The cover 38 is provided with a raised por' tion 54, at'its circular end, having a circular opening. 55 therein. A bridging member 56 extends diametrically across the opening 55 and serves as a means to which a cover 57 for the opening 55 may be secured. s

. The bridging member 56 is illustrated'in detail in Fig. 8 as having a plurality of tapped holes 58 and 59 and a pair of pins 61 that project inwardly into the casing.

-An adjusting screw 62 has screw threaded engagement with the tapped hole 59 and is provided with a knurled head 63 having an i indicating pointer 64 attached that co-operates with a scale 65 on the cover 57.-

An insulating bushing 66 has screw threadedengagement with the cover 38. A guide pin 67 projects through the bushing and into the casing. g I 7 The movement-multiplying mechanism 41 139 comprises a compound rod 68, a pivot 69 attached to one end thereof, a fulcrum wedge 71 and a floating lever 72 that co-operates with the pivot 69 and the Wedge 71.

The compound rod 68 comprises rods. 73 and 74 joined end-to-end by means of a tongue-and-groove connection and a pin 75 that extends through these members to hold them together when subjected to forces of either tension or compression.

The rod 73 is preferably of moulded mate rial, such as bakelite or some other insulating material that is suitable for the purpose. The rod 74 is preferably of such material as has a relatively low temperature co-efficient of expansion. Invar is a material that is useful for our purpose. I

A pivot-supporting member 76 of substantially L-shape is suitably secured to one end of the rod 74 and is provided with a tapped hole with which the pivot 69 has screw threaded engagement.

The pivot 69 comprises a bolt having screw threads thereon and a circular head having a knife edge 77. A bushing 78 is disposed between the member 76 and a nut 79 having screw threaded engagement with the member 69. Thus, the knife edge 77 may be moved either to the right or to the left of its position, as illustrated in Fig. 2, and be locked in any desired position.

The fulcrum wedge'7l illustrated particularly in Fig. 7 is provided with a pair of knife edges 81 for a purpose to be hereinafter set forth and a pair of holes 82 so located at the ends thereofthat they register with the pins 61 of the bridging member 56. The fulcrum wedge 71 may be located in any desired position with respect to the bridging member 56 by means of the screw 62; that is, by turning the knurled head in one direction, the wedge 71 is moved towards the knife edge 77 and if turned in the opposite direction the wedge is moved away from the knife edge.

The lever 72 is provided with a knob 83 at one end that rests against the switch 42, and with a fulcrum shoe 83" at the other end. An intermediate portion of the lever 72 is provided with a hole 84 through which the guide 67extends. The guide pin 67 prevents the lever from moving laterally or longitudinally within the casing comprising the cover 38 and the base 39.

The shoe 83 is provided with a tapered end portion that fits into a slot in the lever 72 and is suitably secured to the lever by means of rivets or pins 85. Two slots 86and 87 are located adjacent the edges of the shoe 83 and serve'to divide the shoe into portions 88 and 89. The portions 88 are bent upwardly and the portions 89 downwardly along the line IX -IX (see Fig. 5) whereby the top face of the portion 89 is substantially-in alinement with the bottom faces of the portions 88 (see Fig. 6). 1

The knife edge 77 of the pivot 69 engages the top face of the portion 89, and the knife edges 81 engage the bottom face of the por tions 88, and it is to be noted from Fig. 2 that the knife edges 81 and 77 are substantially in the same place.

The switch 42 comprises a resilient metallic frame 91 that has a pair of apertures 92 extending longitudinally thereof and adjacent to its cdgesf A central portion of the frame 91 is so bent that a section 93 of substantially W-shape is formed. A portion 94 between the apertures 92 is provided with curved ends 95 which extend away from the plane containing the frameQ'llhe portion 94 being longer than the apertures 92 is, therefore, caused to assume an arched position, substantially as illustrated in Fig. 2.

The switch 42 is secured to the base 48 by means of screws 96 that extend through the base 48 and the section 93 of W-shape. A

washer 97, of suitable insulating material and located on the outside of the base 39, co-operates with the" screws 96 to hold the base 48 in position with respect to the base39.

A terminal screw 98, having a contact 99 at one end thereof, extends through a central portion of the switch base 48 and serves as one terminal 'of the switch 42. A contact 101 is secured to the portion 94 in contact-making relation to the contact 99.

An adjusting screw"102 extends through one end of the frame 91 and has screw threaded engagement with the bushing 49, whereby this end of the frame may be bent towards the bottom of the base 39 to any desired extent. The 'other end of the frame 91 engages the knob 83 carried by the lever 72.

If the ends of the frame 91 or either of them be moved towards the bottom of the base 39, the portion 94 is so bent'that it passes through a state of unstable equilibrium from which it moves with a snap motion thereby disengaging the contact 101 from the contact 99.

The switch illustrated in the drawings, which we prefer to use, is a self-resetting switch that is, it re-engages its contact members from a disengaged position automatical- 1y. However, any other switch may be employed, in which case, it may be found necessary tobias the end of the lever 72, which carries the knob 83, towards the position in which it is maintained, as illustrated in Fig. 2.

' As illustrated in Fig. 1, the circuit-interrupting means 13 is secured to the base 11 by means of the flange 44 and a plurality of suitable bolts or rivets. The rod 73 is secured to the member 18 by means of nuts that are located on each side thereof and extend through the opening 25 in the bar 15.

When the temperature of the ,bar 18 is increased'by reason of current traversing the same or because of increasing ambient temperatures when used in refrigerators and the like, the central portion thereof -moves 1n- I wardy toward the base 14, thereby moving the compound rod 68 into the casing comprising i the cover 38 and the base 39. Thus, the knife edge7 7 is actuated into engagement with the fulcrum shoe 83 which, in turn, upon further expansion of the member 18, is actuated into engagement, with the knife edges 81. On further expansion of the member 18, the lever 72 rocks on the fulcrum knife edges 81 until the knob 83 has actuated the switch to a circuit-opening position, in a manner hereinbefore set forth.

It is to be assumed that the switch 42 controls a, circuit interrupter that breaks the circuit in which the member 18 is included, thereby permitting the member 18 to cool. When the member 18 has cooled sufficiently, the compound rod 68 is moved outwardly, and the lever 72 is actuated to substantially the position illustrated in Fig. 2 by means of its self re-setting switch 42.

When thedevice illustrated in Fig.1 is embodied in a switchboard apparatus for limiting the maximum safe value of current that is permissible totraverse the bus bar 18, the 'scale' 65 may be calibrated in terms of amperes of current.

If it is assumed that the position ofthe pointer 64corresponds to a setting of the thermo-responsive means 11 which will op-- erate in response to a current,flow of 100 amperes, the bus bar 18-will deflect sufliciently to actuate the switch to its circuit-interrupting position.

If it is desired that the 'thermo-responsi ve device 11 shall actuate the switch 42 to a cire cuit-opening position in response, to a current value of 200 amperes, the knurled head 63 is turned in a counter-clockwise direction,

" thereby moving the fulcrum wedge 71 away from the lever-arm shoe 83" along the pins 61. It will then be necessary, before the switch 42' is actuated to its-eircuit-opening position, for'the member 18 to expand a rela-' tively greater amount than in the cases previously mentioned before the knife edge "77 engages the shoe 83 on the knife edges 81' until the lever 72 has actuated the switch' 42 to a circuit-opening. position The larger the amount of current necessary to actuate turned in a clockwise direction? the switch 42 to a circuit-opening position, the moreis the knurled head 6?; turned in a counter-clockwise direction.

-If the device 11 is to be responsive to small 1 er valuesv of current, the knurled head is The pivot 69 made adjustable in orderthat the distance between the knife edges 81 and the knife edge 7 7 may be varied in accordance with any operating differential d'esired. The greater the distance between the knife edges 77 and 83, the greater will be the expansion and contraction required of the member 18 to actuate the lever 72 to cause the switch 42 to move from the circuit-closing position to a circuit-opening position and back to its circuit-closmg positlon.

If the member 18 is secured to the walls of a refrigerator. or an electrically heated device, its expansion and contraction are pro- I duced by changes in temperature to whlch it is subjected. The operationof the device 11, in other respects, is substantially like that which has been previously described. If the device 11 is used for controlling temperatures, the scale 65 may be graduated in terms of temperaturese It is to be assumed that the switch 42' controls either the operation of an artificial refrigerating plant when used to regulate temperatures of refrigerators to control the energization and de-energization of electricheating units when employed for controlling temperatures of ,electric ovens and similar devices.

By our invention, we have. utilized parts employed in switchboard apparatus and similar devices and adapted them to perform the functions of a thermostat in addition to their primary functions.

- bus bar'or a similar member to form a thermostatwiththe walls of a refrigerator or the walls of an electrically heated oven.-

Thus, we have utilized the base of a switchboard, which is Various modifications may be made in the device embodying our invention without departing from the spirit and scope thereof. We desire, therefore, that only such limita-' tions shall be placed thereonas are imposed by the prior art and the appendedclaims. N We claim as our invention:

y 1. The combination with a frame member, abar mounted on said frame and having one end thereof slidably secured thereto, an

initially conditioned member insulatedly mountedron saidbar, and a circuit-controll 1n-g:dev1ce,.of means op eratively associated .with themember for actuating the circuitcontrolling device when a predetermined cur-' v rentcondition obtains in said member.

2. The combination with a relatively fixed support, a metallic member slidably secured 1 thereto, and .a circuit interrupting'.device,

of thermostatic means for actuating the c'ircuit-interrupting device, said means comprising 't he fixed support, and an initially conditioned member secured to metallic memher, said initially conditioned member having a high co-efiicient of expansion relatively to that of the support but having a temperature co-efiicient of expansion substantially equal to that of the metallic member.

3; A thermostatic means comprising a switchboard base, a metallic member slidably secured thereto, a bus bar secured to the metallic member and nieans for passing an electric current through the bus bar. a

4. In a thermoresponsive device, the combination with a switchboard base of relatively non-expanding material, of a currenttraversed bus bar mounted on said base and expansible relatively thereto, an electric control switch, and means for actuating said v switch by said bus bar.

5. In a circuit-protective device, the com bination with a switchboard base of relatively non-expanding material and a control switch mounted on said base, of a current-traversed bus bar mounted on said base and expansible relatively thereto, and means for actuating said switch by the bus bar.

6. In a bus bar circuitrotective device the combination with a swltchboard base oi relatively non-expanding material and a control switch mounted thereon, of a currenttraversed bus bar mounted on said switchboard base and restrained against longitudinal movement and means operatively connecting said switch and bus bar for actuating the switch in response to movement of the bus bar when traversed by a current of predetermined value.

7. In a busbar circuit-protective device, the combination with a switchboard base of relatively non-expanding material and a control switch mounted thereon, of an initially deflected current-traversed bus bar restrained against longitudinal movement, and means for actuating the switch in response to lateral movements of the bus bar. V

8. In a thermo-responsive device, the combination with a switchboard base, a control switch and an initially curved currente traversed bus bar mounted on the switchboard base, of means operatively associated with the bus bar for maintaining it in its initially curved condition, irrespective of variations of the ambient temperature.

In testimony whereof, we have hereunto subscribed our names this 26th day of J anuary,1927,

HENRY D. JAMES. AUGUST J MOTTLAU. 

